A layer discrete particle based soft contact model in corroded rebar monitoring using linear and nonlinear ultrasonic guided waves

In offshore reinforced concrete (RC) structures, the phenomenon of rebar corrosion is widespread, seriously threatening the durability of the structures. However, the issue of rebar corrosion detection especially for the early corrosion situation is also challengeable. It is of great significance to use ultrasonic guided waves (UGWs) for monitoring the situation of the rebar corrosion entire process. In this paper, a mechanical model was used to establish the relationship between different rebar corrosion expansion states and layer-surface contact pressures in the layered RC components with radial cracks. Based on this model, a soft pressure-dependent contact 2D model in Abaqus was used to simulate the local corrosion layer. A linear and nonlinear signal joint analysis (LNSJA) method using PZT-based UGWs was proposed to monitor rebar corrosions, and an LNSJA-based rebar corrosion damage index (RCDI) for corroded RC components was proposed. The proposed method which can effectively detect both the micro- and macro-thickness as well as local area of rebar corrosion layer was validated by the relevant experiment and finite element analysis (FEA).